• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.547-554
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• 2016

This study considered how to estimate the deterioration rate of the track quality index, which represents track geometric irregularity. Most existing studies have used a simple linear regression and regarded the slope of the regression equation as the progress rate. In this paper, we present a Bayesian approach to estimate the track irregularity progress. This Bayesian approach has many advantages, among which the biggest is that it can formally include the prior distribution of parameters which can be derived from historic data or from expert experiences; then, the rate can be expressed as a probability distribution. We investigated the possibility of applying the Bayesian method to the estimation of the deterioration rate by comparing our bayesian approach to the conventional linear regression approach.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.66-72
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• 2014

This paper introduces an asynchronous multiple radar fusion algorithm for space object tracking. To estimate orbital motion of space object, a multiple radar scenario which jointly measures single object with different sampling time indices is described. STK/ODTK is utilized to determine realization of orbital motion and joint coverage of multiple radars. Then, asynchronous fusion algorithm is adapted to enhance the estimation performance of orbital motion during which multiple radars measure the same time instances. Monte-Carlo simulation results demonstrate that the proposed asynchronous multi-sensor fusion scheme better than single linearized Kalman filter in an aspect of root mean square error.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.629-635
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• 2012

Tracked robots usually have poor localization performance because of slippage of their tracks. This study proposes a new localization method for tracked robots that uses fuzzy fusion of stereo-camera-based visual odometry and encoder-based wheel odometry. Visual odometry can be inaccurate when an insufficient number of visual features are available, while the encoder is prone to accumulating errors when large slips occur. To combine these two methods, the weight of each method was controlled by a fuzzy decision depending on the surrounding environment. The experimental results show that the proposed scheme improved the localization performance of a tracked robot.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.173.1-173.1
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• 2012

천리안 위성 원격측정명령계 RF부는 위성 장착 이후 발사 전까지 여러 단계의 위성체레벨 기능시험을 거치며 요구 성능을 만족하는지를 충분히 확인하였다. 위성 발사후부터 정상궤도 진입 후에 발사전 원격측정명령계 RF가 원하는 요구 기능 및 성능을 만족하고 있는지를 확인하는 궤도운용시험이 수행되었다. 본 논문은 원격측정명령계 RF부의 궤도운용시험 계획에 따라 수행하여 얻어진 시험 결과에 대한 분석에 대한 것이다. 먼저 발사 후 LEOP 동안 원격명령이 정상적으로 수신되고 수행되는지 확인하였다. 그 이후 원격명령이 언락되는 수신 파워 임계(Threshold) 입력 레벨 확인을 확인하였으며 원격측정 다운링크 주파수 변이가 요구범위에 있는지 확인하였으며, 수신신호 스펙트럼 측정을 통해 TM EIRP를 추정한 결과 링크 버짓 마진 대비 추가적인 마진이 있음을 확인하였으며 또한 TM 송신 신호 변조지수가 추정범위 안에 있는지를 확인하였다. 그리고 레인징 시험을 통해 수신기 및 레인징 기능이 정상적으로 동작하고 있음을 확인하였다. 이 궤도운용시험 결과는 후속 정지궤도복합위성 원격측정명령계 RF부 궤도운용시험을 위한 비교 자료로 활용될 것이다.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.304-308
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• 2010

This paper presents a methodology for identifying track irregularity using a wavelet transfer function. An equivalent wavelet SISO (single-input single-output) transfer function is defined by the measured track geometry and the acceleration data measured at a bogie of a train. All the measured data with various sampling frequencies were rearranged according to the constant 25cm reference recording distance of the track recording vehicle used in the field. Before applying the wavelet transform, measured data were regressed by eliminating those out of the range. The inverse wavelet transfer function is also formulated to estimate track geometry. The closeness of the estimated track geometry to the actual one is evaluated by the coherence function and also by FRF (frequency response function). A track irregularity index is defined by comparing the variance of the estimation error from the intact condition and that from the current condition. A simulation study has been carried out to examine the proposed algorithm.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.24.1-24.1
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• 2011

2006년도부터 개발을 시작한 한국천문연구원 궤도 전파 및 추정(KASI Orbit Propagator and Estimator: KASIOPEA)소프트웨어는 다양한 과제와 연관되어 개발을 추진했다. 초기 이 소프트웨어는 GNSS 자료처리를 염두에 두고 개발을 시작하였으나, 현재 한국천문연구원 우주측지연구그룹에서 추진하는 GNSS 자료처리와 별도로 한국천문연구원에서 1986년도부터 개발을 시작한 우주물체 궤도 추적, 전파 및 추정을 새로운 개발 목표로 재추진하게 되었다. 이 소프트웨어의 개발 요구사항은 광학감시 체계의 운영을 전제로 하고 있어 전파 및 레이저 위성 추적 시스템과 별도로 정의되어 있다, 이 요구사항 분석이 완료되면 이 소프트웨어의 최종 성능에 대한 예비 결정이 이뤄질 것으로 사료된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2603-2609
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• 2000

In this paper, track tension estimation methods are developed for tracked vehicles which are subject to various maneuvering tasks such as longitudinal driving on sloping and/or rough roads. The information of the track tension is very important for the tracked vehicles because the track tension is closely related to the maneuverability and the durability of the tracked vehicles. A modified 3 DOF dynamics model is derived for the tracked vehicles and is utilized for estimating the tractive force and track tension for the longitudinal driving case. The tension estimation performance of the proposed methods is verified through the simulation of the Multi-body Dynamics tool. The simulation results demonstrate the effectiveness of the proposed method under various maneuvering tasks of the tracked vehicles.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.115-121
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• 2000

In this paper, track tension estimation methods are developed for tracked vehicles which are subject to various maneuvering tasks such as turning and pivoting on flat road. The information of the track tension is very important for the tracked vehicles because the track tension is closely related to the maneuverability and the durability of the tracked vehicles. Kinetic models for the six road-wheels are obtained and used for calculating the track tension around the sprocket. This method does not require the tuning of the turning resistance, which makes it difficult to estimate the track tension in turning. The tension estimation performance of the proposed methods is verified through the simulation of the Multi-body Dynamics tool. The simulation results demonstrate the effectiveness of the proposed method under steering and pivoting of the tracked vehicles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1126-1131
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• 2008

This paper applies the Orbital Geometry-based Bias Estimation Algorithm to the magnetometer measurement data of KOMPSAT-1 and 2 and analyzes the induced magnetic field bias caused by the solar panels and electronics boxes in spacecraft bus. This paper reveals that the estimation and correction of the induced magnetic field bias copes with the aging process of magnetometer and makes it possible to carry on the satellite mission by extending its lifetime.

• Bulletin of the Korean Space Science Society
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• 2002.05b
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• pp.40-40
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• 2002